Commentary
1
1 NO 4 - 1986 REPRODU'~TiB[L/T3" OF CAROTID DOPPLER 7'ESITN(; 473 CONCLUSION Serial examination demonstrated a variation of peak systolic frequency for both the 5 MHz and 8 MHz probes. Our data suggest that studies from the same center az different times, or different tes- ting centers, need tt~ be standardized as to the emit- ting frequency of the ex~mining probe. Once these techniques are standardized, serial examinations over time should be valid an provide an index of evolving carotid s~.eaosis. In our experience, reliabil- ity is best achieved with a 5 MHz probe. REFERENCES 1. SPENCER MP, REID .IM. Quantification of carotid stenosls with continous-wave {C-W) Doppler ultrasound. Stroke 1979 ; 10 : 326. 2. ZWEIBEL W3, ZAGZEBSK] JA, CRUMMY AB, HIR- SCHER M. Correlation el peak Doppler frequency with lumen narrowing in carotid stenosis. Stroke 1982 ; 1-~' : 38(,. 3. BARNES RW. NIX L, R[TTGERS SE. Audible interpreta- tion of carotid Doppler signals. An improved technique to de- fine carotid artep,, disease Arch Sur~ 1981 ; 116 : 1185. a. HAYES AC. BAKER WEI. Noninvasi',e laboratory e~alua- tion. bz : BAKER WH, ed. Diagnosis and IYeafme~t of Caro- lid 4rtery Disease, 2rid ed.. New York : futara Publishing Ce., 1985 : 1-96. Comm..ntary This paper Izighlights a serious problem in the use c~f hand-held continuous wave Doppler uhras'ound probes for detecting and Jollc~wir~g the development of carotid arz'ery stenosis. While the aztthors" recognize the importance of probe angle in the determination of Doppler-shif? frequency, they chose to ~gnore its ef- fect when using this technique. The value of cosine 0 changes rapidly and sign!fi- cantlv in the range f) = 40~ to 0 = 6'(~'. Cosin~ 4(~' = O. 7660, cosine 6'0" = 0. t 736. Variations of probe angle alone between the range 40" and 80" in an otherwise constant system would account for peak frequency shifts that change by a factor of nearly 4.5 (0.7660 + 0.1736). A more conservative estbnare of range of probe angle changes 45 '~ to 7(r' yields a factor t~f 2. Anyone eontempl'ating follow.up of srenosis devel.. opment b); transcutaneous continuous-wave Doppler owes both to themseh,es and their patients to utilize a system which provides adequate estimation of probe angle to the axis of the vessel under examination (not probe angle to skin). There is mountin'r evidence that the morphology of the plaqrte is ~)t" greater significance than the loss of cross-sec~ional area. Whether a stenosis is 65 % or 75 % is of little consequence compared to the compo- sition c;f the lesion. A soft thrombotic plaque repre- senting a 45 % stenosis may deserve more freqztent follow-up than a dense, calcified or fibrotic lesion re- presenting a 75 cYc ster~osis. Knowledge of the composition of asymptorn,~tic plaque may be used to reduce the frequency of fol- low-up studies of stable plaque and intensify the at- tention paid to plaques with potentially; unstable (sc~ft, thrombotic, hemorrhagic, etc.) characteristics. Roger Higgins, PhD. Detroit, Michigan
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Transcript of Commentary
�89 1 NO 4 - 1986 REPRODU'~TiB[L/T3" OF C A R O T I D D O P P L E R 7'ESITN(; 473
CONCLUSION
Serial examination demonstrated a variation of peak systolic frequency for both the 5 MHz and 8 MHz probes. Our data suggest that studies from the same center az different times, or different tes- ting centers, need tt~ be standardized as to the emit- ting frequency of the ex~mining probe. Once these techniques are standardized, serial examinat ions over time should be valid an provide an index of evolving carotid s~.eaosis. In our experience, reliabil- ity is best achieved with a 5 MHz probe.
REFERENCES
1. SPENCER MP, REID .IM. Quantification of carotid stenosls with continous-wave {C-W) Doppler ultrasound. Stroke 1979 ; 10 : 326.
2. Z W E I B E L W3, Z A G Z E B S K ] JA, C R U M M Y AB, HIR- SCHER M. Correlation e l peak Doppler frequency with lumen narrowing in carotid stenosis. Stroke 1982 ; 1-~' : 38(,.
3. BARNES RW. NIX L, R [TTGERS SE. Audible interpreta- tion of carotid Doppler signals. An improved technique to de- fine carotid artep,, disease Arch Sur~ 1981 ; 116 : 1185.
a. HAYES AC. B A K E R WEI. Noninvasi ' ,e laboratory e~alua- tion. bz : B A K E R WH, ed. Diagnosis and IYeafme~t of Caro- lid 4rtery Disease, 2rid ed.. New York : f u t a r a Publishing Ce. , 1985 : 1-96.
Comm..ntary
This paper Izighlights a serious problem in the use c~f hand-held continuous wave Doppler uhras'ound probes for detecting and Jollc~wir~g the development of carotid arz'ery stenosis. While the aztthors" recognize the importance of probe angle in the determination of Doppler-shif? frequency, they chose to ~gnore its ef- fect when using this technique.
The value of cosine 0 changes rapidly and sign!fi- cantlv in the range f) = 40 ~ to 0 = 6'(~'. Cosin~ 4(~' = O. 7660, cosine 6'0" = 0. t 736.
Variations of probe angle alone between the range 40" and 80" in an otherwise constant system would account for peak frequency shifts that change by a factor of nearly 4.5 (0.7660 + 0.1736). A more conservative estbnare of range of probe angle changes 45 '~ to 7(r' yields a factor t~f 2.
Anyone eontempl'ating follow.up of srenosis devel.. opment b); transcutaneous continuous-wave Doppler
owes both to themseh,es and their patients to utilize a system which provides adequate estimation of probe angle to the axis of the vessel under examination (not probe angle to skin).
There is mountin'r evidence that the morphology of the plaqrte is ~)t" greater significance than the loss of cross-sec~ional area. Whether a stenosis is 65 % or 75 % is of little consequence compared to the compo- sition c;f the lesion. A soft thrombotic plaque repre- senting a 45 % stenosis may deserve more freqztent follow-up than a dense, calcified or fibrotic lesion re- presenting a 75 cYc ster~osis.
Knowledge of the composition of asymptorn,~tic plaque may be used to reduce the frequency of fol- low-up studies of stable plaque and intensify the at- tention paid to plaques with potentially; unstable (sc~ft, thrombotic, hemorrhagic, etc.) characteristics.
Roger Higgins, PhD. Detroit, Michigan
